The primary defense against surgical pathogens is oxidative killing by neutrophils. This reaction critically depends on tissue oxygen tension. It is therefore unsurprising that subcutaneous tissue oxygen tension (PsqO2) is inversely correlated with the risk of surgical wound infection. As might be expected, supplemental perioperative oxygen administration increases tissue oxygen partial pressure (compared with an FIO2 of 30%) and decreases wound infection risk. While 100% oxygen is associated with atelectasis and pulmonary inflammation, we and others have shown that 80% oxygen is not.